The Treasury of the Athenians is one of the most important and impressive buildings of the temenos of Apollo. Standing next to the bouleuterion, seat of the Delphic senate, and opposite the treasuries of the Knidians and the Syracusans, it dominated the Sacred Way. This small building contained trophies from important Athenian victories and other votive objects dedicated to the sanctuary.

The treasury, which was built by the Athenian republic in the late sixth or early fifth centuries BC, is thought to express the victory of democracy over tyranny. A slightly different interpretation, based on Pausanias's description, states that the treasury commemorated the battle of Marathon of 490 BC, when the Athenian army repelled the Persians.

The treasury, a small, Doric building in Parian marble, is shaped like a temple in antis, as are most treasuries. Its relief decoration is a remarkable example of late Archaic sculpture, comparable in elegance, lightness of the analogies, vigorous, solid movement and daring stances to early Attic Red Figure vase painting. The frieze depicts the exploits of Hercules (back and north facade) and of Theseus (front and south facade). The juxtaposition of the two heroes symbolizes the change of regime and the establishment of democracy in Athens. Indeed, Theseus became a prevalent subject in fifth century BC iconography, while Hercules dominated sixth century art. The building stands on a terrace whose south and main fa?ades, those dominating Sacred Way, end in a triangular buttress. This is where the Athenians exposed the spoils from the battle of Marathon and other trophies kept inside the treasury during great festivals and processions.

Several inscriptions on the building's walls inform us on ancient festivals and customs, namely the Pyrphoria, the Tripodiphoria, the Pythais and the Dodecais, the four official processions of the Athenians at Delphi. Another inscription near the eastern corner of the south wall is extremely useful for the study of ancient music, since it contains two unique hymns to Apollo, the only extant Greek texts with musical annotations, now on display in the Delphi Archaeological Museum. Inside the treasury, are inscriptions containing important honorary decrees dating from the third century BC and later, as well as the names of pawnbrokers who used the premises in later years.

The Treasury of the Athenians was the only Delphic monument that still preserved much of its ancient fabric in the early twentieth century, and so was re-erected by the French School in 1906 with funds granted by the mayor of Athens, Spyros Merkouris. The original frieze is in the Delphi Archaeological Museum, the sculptures in situ being casts.